Seasonal Thermocline Research Articles

Silicon in waters of the Sevastopol Bay in spring 2008

On the basis of field studies executed in May 2008, we performed the analysis of the distribution of silicon in waters of the Sevastopol Bay under conditions of the formation of a seasonal thermocline. We discuss differences in the distributions of silicon in the surface and bottom layers, including the zone of mixing of river and sea waters. We noticed a significant difference in values of the coefficients of correlation between the concentration of silicon and the salinity for the surface and bottom layers. For bottom layer, we obtain large values of the coefficients of correlation between the concentration of silicon and other hydrochemical characteristics which are explained by the influence of the processes of transformation of organic substance.

Inertia-gravity waves beyond the inertial latitude. Part 1. Inviscid singular focusing

The paper is concerned with analytical study of inertia-gravity waves in rotating density-stratified ideal fluid confined in a spherical shell. It primarily aims at clarifying the possible role of these motions in deep ocean mixing. Recently, it was found that on the ‘non-traditional’ β-plane inertia-gravity internal waves can propagate polewards beyond their inertial latitude, where the wave frequency equals the local Coriolis parameter, by turning into subinertial modes trapped in the narrowing waveguides around the local minima of buoyancy frequencyN. The behaviour of characteristics was established: wave horizontal and vertical scales decrease as the wave advances polewards and tend to zero at a latitude corresponding to an attractor of characteristics. However, the basic questions about wave evolution, its quantitative description and the possibility of its reflection from the critical latitude remain open. The present work addresses these issues by studying the linear inviscid evolution of finite bandwidth wavepackets on the ‘non-traditional’ β-plane past the inertial latitude for generic oceanic stratification. Beyond the inertial latitude, the wave field is confined in narrowing waveguides of three distinct generic types around different local minima of the buoyancy frequency. In the oceanic context, the widest is adjacent to the flat bottom, the thinnest is the upper mixed layer, and the middle one is located between the seasonal and main thermocline. We find explicit asymptotic solutions describing the wave field in the WKB approximation. As a byproduct, the conservation of wave action principle is explicitly formulated for all types of internal waves on the ‘non-traditional’ β-plane. The wave velocities and vertical shear tend to infinity and become singular at the attractor latitude or its vicinity for both monochromatic and finite bandwidth packets. We call this phenomenonsingular focusing. These WKB solutions are shown to remain valid up to singularity for the bottom and mid-ocean waveguides. The main conclusion is that even in the inviscid setting the wave evolution towards smaller and smaller horizontal and vertical scales is irreversible: there is no reflection. For situations typical of deep ocean, a simultaneous increase in wave amplitude and decrease of vertical scale causes a sharp increase of vertical shear, which may lead to wave breaking and increased mixing.

Snapshot observation of the physical structure and stratification in deep-water of the South Caspian Sea (western part)

Abstract. The physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) adjacent to Anzali Port (AP) are investigated. CTD profiles were conducted along a transect perpendicular to the coastline on 13 stations from the coast down to 720 m on 22 January 2008. According to the results the continental shelf waters are located in the surface mixed layer. The surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m Freshwaters inflow of local rivers is clearly seen outside the continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 300 m seems to be a threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite the small variations, stability is positive in the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, two different water masses are separable in cold phase. Snapshot observations of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.

Fluorescence measured in situ as a proxy of CDOM absorption and DOC concentration in the Baltic Sea

This study presents results from field surveys performed in 2008 and 2009 in the southern Baltic in different seasons. The main goal of these measurements was to identify the empirical relationships between DOM optical properties and DOC. CDOM absorption and fluorescence and DOC concentrations were measured during thirteen research cruises. The values of the CDOM absorption coefficient at 370 nm aCDOM(370) ranged from 0.70 m −1 to 7.94 m, and CDOM fluorescence intensities (ex./em. 370/460) IFl, expressed in quinine sulphate equivalent units, ranged from 3.88 to 122.97 (in filtered samples). Dissolved organic carbon (DOC) concentrations * This study was funded by the Polish Ministry of Science and Higher Education through grant No. NN 306-2942-33 for the research project entitled ‘Spectral properties of CDOM absorption and fluorescence and their relationship with Dissolved Organic Carbon concentration in the Baltic Sea’. The principle investigator was Piotr Kowalczuk. The research infrastructure, including access to the research vessel r/v ‘Oceania’, was provided by the Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland. Partial support for this study was also provided by the project Satellite Monitoring of the Baltic Sea Environment – SatBaltyk, co-founded by the European Union through European Regional Development Fund contract No. POIG 01.01.02-22-011/09. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 432 P. Kowalczuk, M. Zablocka, S. Sagan, K. Kulinski ranged from 266.7 to 831.7 μM C. There was a statistically significant linear relationship between the fluorescence intensity measured in the filtered samples and the CDOM absorption coefficient aCDOM(370), R 2 = 0.87. There was much more scatter in the relationship between the fluorescence intensity measured in situ (i.e. in unprocessed water samples) and the CDOM absorption coefficient aCDOM(370), resulting in a slight deterioration in the coefficient of determination R = 0.85. This indicated that the presence of particles could impact fluorometer output during in situ deployment. A calibration experiment was set up to quantify particle impact on the instrument output in raw marine water samples relative to readings from filtered samples. The bias calculated for the absolute percentage difference between fluorescence intensities measured in raw and filtered water was low (−2.05%), but the effect of particle presence expressed as the value of the RMSE was significant and was as high as 35%. Both DOM fluorescence intensity (in raw water and filtered samples) and the CDOM absorption coefficient aCDOM(370) are highly correlated with DOC concentration. The relationship between DOC and the CDOM absorption coefficient aCDOM(370) was better (R = 0.76) than the relationship between DOC and the respective fluorescence intensities measured in filtered and raw water (R = 0.61 and R = 0.56). The seasonal cycle had an impact on the relationship between DOC and CDOM optical properties. The hyperbolic relationships between aCDOM(370) vs. carbon-specific absorption coefficient a∗CDOM(370), and IFl vs. the ratio of fluorescence intensity to organic carbon concentration IFl/DOC were very good. The discharge and mixing of riverine waters is a primary driver of variability in DOC and CDOM optical properties in the surface waters of the southern Baltic Sea, since all the parameters considered are negatively correlated with salinity. It was found that there was a positive trend of increasing values of DOM optical parameters with salinity increase (within a range of 8–12) in deep water below the permanent pycnocline. Evidence is also presented to show that late-summer photodegradation was responsible for the depletion of CDOM florescence intensities in the mixed layer above the seasonal thermocline. It was further demonstrated that the DOC concentration increases in the stagnant waters of the Baltic Sea deeps. The Integrated Optical-Hydrological Probe, which registers high-resolution vertical profiles of salinity, temperature, CDOM and the optical properties of water, confirmed that DOM optical proxies can be used in studies of DOM biogeochemical cycles in the Baltic Sea.

Session 1

The assemblages of the demersal and deep-water fish assemblages of the Cabo Verde archipelago are described for the first time from a total of 20 longline hauls that extends from coastline to 1200 m water depth. A total of 98 species from 47 different families were caught, and despite the changes of biogeographic affinities with depth, the majority of the species are from a Subtropical and Tropical origin or have a broad geographic distribution (Wide and Amphiatlantic distributions) with small affinities with the Macaronesian islands and the Mediterranean. Depth distribution profiles show a clear turnover of species with depth, and an increase in the depth distribution range of the deeper living species. Furthermore, the indices of species abundance, biomass and the number of species caught, significantly decreased with increasing depth. Four main fish assemblages in a depth-aligned structure are proposed in the present work. A shelf assemblage mainly distributed above the 150 m depth strata, a shelf-break/upper-slope assemblage mainly between the 150–350 m depth strata, a deep/upper-slope assemblage between the 300–600 m depth strata, and a mid- deep/mid-slope assemblage mainly distributed below the 600 m. Species abundances and diversity found below 200 m is relatively low compared with shallow waters. The observed depth zonation of the slope assemblages, roughly agrees with the expected occurrence or influence of different water masses: shelf and surface mixing and seasonal thermocline depth zone, the depth range of occurrence of the intermediate waters (North Atlantic Central Water—NACW), the South Atlantic Central Water—SACW), and Atlantic Equatorial Water—AEW), a mixing or overlapping zone of previous intermediate water masses with the Antarctic Intermediate Water (AAIW), and the Mediterranean Outflow Water (MOW), and a deeper zone where the AAIW predominate.

Processes responsible for the formation and maintenance of sub-surface chlorophyll maxima in the Gulf of Finland

Vertical cross-sections of temperature, salinity and Chl a fluorescence distributions in the Gulf of Finland were mapped on 11, 19–20 and 25 July 2006. The sub-surface Chl a maximum layers with thickness varying between 1.5 and 9 m and intensity up to 7.6 μg l −1 were observed in the lower part of the seasonal thermocline within the depth range of 14.5–35 m. Nutrient (PO4 3−, NO2 − + NO3 −) analyses of water samples collected from the thermocline revealed the coincidence of the location of Chl a maxima and nutriclines. We suggest that the observed Chl a maxima were formed by dinoflagellate Heterocapsa triquetra capable for vertical migration and nutrient uptake in dark. The upward flux of nutrients caused by estuarine circulation and vertical turbulent mixing created favourable conditions for the formation and maintenance of sub-surface Chl a maxima. We explain the observed horizontal patchiness of sub-surface Chl a maxima by meso-scale processes – by the accumulation of phytoplankton along the depressed isopycnals at the base of anti-cyclonic circulation cells and by the horizontal convergence of waters in the downwelling area.

Seasonal versus permanent thermocline warming by tropical cyclones

Recent studies suggest that the enhanced upper ocean mixing caused by tropical cyclones significantly contributes to the ocean heat transport. However, existing studies that try to quantify this contribution make the assumption that all heat pumped below the mixed layer by tropical cyclones is finally released in higher latitudes. Tropical cyclones occur primarily during summer and early fall, when the ocean mixed layer is generally shallow. As the mixed layer deepens in the following winter, any warm anomaly deposited within the seasonal thermocline will be reabsorbed by the mixed layer and lost to the atmosphere. Analysis of satellite sea surface temperature and sea surface height data, together with climatological subsurface ocean data, suggests that only about one quarter of the heat that is mixed downward by tropical cyclones eventually makes it into the permanent thermocline.

The Vertical Structure of Eddy Heat Transport Simulated by an Eddy-Resolving OGCM

Abstract The vertical structure of meridional eddy heat transport (EHT) of the North Pacific was investigated by analyzing the results from an eddy-resolving ocean general circulation model (OGCM) with a horizontal resolution of , while comparing with previous simulation results and observation data. In particular, the spatial and temporal variation of the effective depth of EHT He was investigated, which is defined by the depth integrated EHT (D-EHT) divided by EHT at the surface. It was found that the annual mean value of He is proportional to the eddy kinetic energy (EKE) level at the surface in general. However, its seasonal variation is controlled by the mixed layer depth (MLD) in the extratropical ocean (>20°N). Examination of the simulated eddy structures reveals that the temperature associated with mesoscale eddies is radically modified by the surface forcing in the mixed layer, while the velocity field is not, and the consequent enhanced misalignment of temperature and velocity anomalies leads to the radical change of EHT across the seasonal thermocline.

Morphological, geochemical, and ecological differences of the extant menardiform planktonic foraminifera Globorotalia menardii and Globorotalia cultrata

Taxonomic consistency is the prerequisite for any foraminiferal study. In particular, interpretation of planktonic foraminiferal geochemical data requires consistent selection of monospecific tests due to varying habitats of different species. In order to exemplify the impact of slightly varying morphological characteristics on geochemical signatures, we investigated three basic shape dimensions, test weights, stable isotope values, and Mg/Ca ratios of Globorotalia menardii and Globorotalia cultrata, which are often grouped or referred to as synonyms. Along with visual distinction, encrusted G. menardii is distinguished from shiny G. cultrata by its on average doubled test weight, when referring to the same maximum diameter. More elongated and flattened G. cultrata calcifies within the deeper mixed layer, which applies also for the initial calcification of G. menardii. Final encrustration of G. menardii after vertical migration is suggested to take place close to the bottom of the seasonal thermocline. Combined Mg/Ca ratios versus calcification–temperature calibration provides a reliable tool for monospecific thermal reconstructions for the seasonal thermocline ( G. menardii) and the deeper mixed layer ( G. cultrata).

Seasonal change of oceanographic conditions and chlorophyll a vertical distribution in the southwestern Okhotsk Sea during the non-iced season

Seasonal changes in oceanographic conditions related to primary productivity was investigated in the southwestern Okhotsk Sea during non-iced seasons, using the observation data conducted in 2000∼2006. Based on hydrographic characteristics, the studied area could be classified into two regions, the Coastal Region which is influenced under the Soya Warm Current and the Forerunner Water of the Soya Warm Current, and the Offshore Region where the Intermediate Cold Water was located in the subsurface layer. This study is the first report on seasonal change of nutrient and chlorophyll a concentrations in the offshore region of the southwestern Okhotsk Sea. Variability of concentrations of chlorophyll a and nutrients is temporally and regionally high in the Coastal Region. The maximum chlorophyll a concentration in April was observed at the surface layer of both regions. The most remarkable feature on the vertical structure in the Offshore Region was the consistent existence of the Intermediate Cold Water and the development of seasonal thermocline in the subsurface layer during summer and autumn. The stratification formed within the euphotic zone in the Offshore Region resulted in the formation of the subsurface chlorophyll a maximum (SCM) from May to October. Throughout the research period, although less amplitude of nutrients at the surface was observed in the Coastal Region than that in the Offshore Region, comparable amplitude of chlorophyll a concentration was observed between regions. These results suggested differences of environmental conditions for primary production between the two regions. Depending on the presence of SCM, relationships between chlorophyll a concentration at the sea surface and chlorophyll a standing stock within the euphotic layer were different. At most stations with SCM, the surface chlorophyll a concentration was lower than 0.6 mg m-3. This suggests that the presence of SCM and the chlorophyll a standing stock within the euphotic layer may be estimated using the surface chlorophyll a concentration from spring to autumn in the studied area.

10.1007/s11491-008-1016-4

During the last ten years, autonomous drifting platforms for data collection (drifters) equipped with Argos satellite communication devices have become one of the main components for the observation system in the upper layer of the ocean and surface atmosphere. This article presents the results of the Black Sea drifter monitoring in 2002–2006 within a number of international programs and projects. During this period, about 70 drifters manufactured by NPF Marlin-Yug Ltd. (Sevastopol, Ukraine) were deployed in the western part of the Black Sea. The drifters were mainly standard barometric Lagrangian tracers and a part of them were principally new temperature profiling buoys. Unique long-term data were obtained about the circulation of the surface currents and the dynamics of the temperature stratification within the seasonal thermocline and the cold intermediate layer.

Observation of near‐inertial wave reflections within the thermostad layer of an anticyclonic mesoscale eddy

Moored current observations in the southwestern East/Japan Sea of 16.5 months duration clearly captured two episodes of downward phase propagation (upward energy propagation) of near‐inertial waves (NIWs). Time series of temperature and velocity from the mooring and ancillary information indicate that the mooring was located near the center of an anticyclonic eddy during these events. Considering the typical vertical structure of quasi‐permanent eddy features in the region, the observed downward phase propagation appeared to occur within the seasonal thermocline and upper thermostad of the anticyclonic mesoscale eddy. Ray tracing simulation of NIW using the observed subinertial currents suggests that the upward energy propagation is caused by the reflection of the NIWs within the thermostad of the anticyclonic eddy, where the effect of the vertical shear of subinertial horizontal currents is larger than the buoyancy effect in controlling the propagation of NIWs.

Deep ocean exchange with west-European shelf seas

Abstract. We review mechanisms and studies of exchange between the north-east Atlantic and the adjacent shelf seas. Well-developed summer upwelling and associated filaments off Portugal and north-west Spain give exchange O(3 m2/s per unit length of shelf). Prevailing westerly winds further north drive exchange O(1 m2/s). Poleward flow along most of the upper slope has associated secondary circulation O(1 m2/s), meanders and eddies. Eddies are shed from slope waters into the Bay of Biscay, and local exchanges occur at shelf spurs and depressions or canyons (e.g. dense-water cascading of order 1 m2/s). Tidal transports are larger, but their reversal every six hours makes exchange largely ineffective except where internal tides are large and non-linear, as in the Celtic Sea where solitons carry water with exchange O(1 m2/s). These various physical exchanges amount to an estimated 2–3 m2/s per unit length of shelf, between ocean and shelf. A numerical model estimate is comparable: 2.5×106 m3/s onto and off the shelf from Brittany to Norway. Mixing controls the seasonal thermocline, affecting primary production and hence fluxes and fate of organic matter. Specifically, CO2 take-up by primary production, settling below the thermocline before respiration, and then off-shelf transport, make an effective shelf-sea "pump" (for CO2 from the atmosphere to the deep ocean). However, knowledge of biogeochemical fluxes is generally sparse, giving scope for more measurements, model validation and estimates from models.

River‐induced particle distribution in the northwestern Black Sea (September 2002 and 2004)

Observations from two comprehensive oceanographic surveys on the northwestern Black Sea are analyzed to reveal the hydrological characteristics of the shelf area around the Danube delta in relation to particulate matter dynamics. These processes have broader implications on flows through the adjacent complex strait system. The surveys cover both a period of high (September 2002) and low (September 2004) discharge of the Danube River. The resulting low‐salinity waters generally occupied the upper 10–15 m within the 20–30 m thick warm layer that was separated by deeper cooler waters through a sharp thermocline. The buoyant plume was influenced by the discharge conditions and the prevailing wind patterns. The plume structure was identified using in situ bottle data, continuous beam transmission and fluorescence profiles, and satellite remotely sensed data. Particulate matter concentration values correlated with low‐salinity riverine waters and their maxima were recorded in the immediate vicinity of the Danube branches, decreasing rapidly toward the open sea. The preferred particle transport pathway in 2002 was along a narrow strip near the coast, with a south‐southwest direction, favored by the strong northeasterlies which predominated prior to the cruise. Low‐salinity waters and riverine particles in 2004 were characterized by mostly offshore removal, attributed to calmer northwesterlies prior to the survey. Changes in ambient stratification due to wind‐driven vertical displacements of the seasonal thermocline appeared to also influence the plume dynamics. The downwelling (upwelling) conditions that prevailed in 2002 (2004) were revealed in both the in situ vertical profile temperature measurements and the satellite‐derived sea surface temperature patterns.

Interannual variability in the subseasonal northward excursion of the Baiu front

The Baiu front, a quasi-stationary front that appears in early boreal summer near the northwestern rim of the subtropical Pacific high, shows interannual variability characterised by polarity changes in precipitation anomalies during the subseasonal northward excursion in the western North Pacific (WNP). These changes are forced by motion over the fixed surface divergence/convergence anomalies in the WNP, which are regulated by the atmospheric bridge or the Pacific–East Asian (PEA) teleconnection. The PEA teleconnection is caused by the tropical sea surface temperature anomalies (SSTAs) associated with the El Nino/Southern Oscillation. The upper ocean mixed layer depth (MLD) is crucial in regulating the SSTAs in the WNP. In the tropical WNP (lower than 20°N), the large MLD (and hence large heat capacity in the upper ocean) can maintain the SSTAs for about half-a-year. In the mid-latitude WNP (higher than 20°N), the development of the seasonal thermocline in early summer reduces the heat capacity, whereas the atmospheric variation modifies the SSTAs within a season. The MLD is regarded as an important parameter that controls the strength and time scale of the air–sea feedback, and the latitude of 20°N approximately separates regions where the oceanic thermal properties are active or passive for the early-summer atmospheric circulations in the WNP. Copyright © 2009 Royal Meteorological Society

On phosphate pumping into the surface layer of the eastern Gotland Basin by upwelling

Hydrographic, current, and nutrient measurements were performed on board of the R/V Poseidon in the eastern Gotland Basin from 12 to 21 July 2007, complemented by satellite measurements of sea surface temperature and chlorophyll-a and by measurements of turbulent dissipation. The main aim of the investigations was to elucidate the pathways of phosphate from the intermediate winter water into the surface mixed layer and how this phosphate flux fosters phytoplankto growth. The deep water of the Gotland Basin was exposed to an enduring stagnation phase resulting in a nitrogen to phosphorus ratio very much lower than the Redfield ratio. The intermediate winter water was completely depleted of nitrate but contained a phosphate pool of about 0.40 µM. The surface mixed layer had a mean depth of about 18 m and water temperature of 16 °C and was depleted of both nitrate and phosphate. The average of photosynthetically active radiation during the cruise was about 700 µE/(m²s) at the sea surface. Three pulses of westerly wind with maximum wind speed of about 15 m/s forced upwelling during the cruise at the east coast of Gotland and downwelling at the Latvian coast. The corresponding eastward Ekman offshore transport moved surface water within about three days through the coastal boundary layer and in roughly 50 days across the Gotland Basin. Two mesoscale eddies were observed off the south eastern coast of Gotland which supported upwelling filaments near the southern tip of this island. Within the coastal boundary layer, the upwelling transported phosphate from the intermediate winter water into the surface layer off Gotland where it was mixed with the phosphate depleted surface water. Generally, the upwelled phosphate was taken up by the plankton community of the surface mixed layer already within the coastal boundary layer and transformed completely into the particulate and dissolved organic phase. However, at sites where upwelling filaments develop, dissolved phosphate is transported over a distance of about three times the internal Rossby radius in offshore direction. The phosphate transport into the surface mixed layer of the eastern Gotland Basin by upwelling exceeded the corresponding transport by turbulent mixing through the seasonal thermocline by about one order of magnitude during typical summerlike wind conditions.

A Study on Concentrations of Dissolved Oxygen and Chlorophyll-a in the Coastal Waters of Babolsar

Problem statement: Dissolved Oxygen (DO) and Chlorophyll-a (Chl-a) are two vital requirements for marine ecosystems. Nowadays, discharge of large amounts of industrial, agricultural and urban wastes threats the Caspian Sea (CS) environment. With regard to the elevation of nutrient contents, average of DO concentrations in the deeper layers of the CS is reducing. On the other hand, increased amounts of phytoplankton in water bodies in reaction to the enhancement of nutrient supply can have severely damaging effects on the marine environment. According to the importance of DO and Chl-a in marine ecosystems of the Caspian, we attempted to investigate the distributions of DO and Chl-a in the southern coastal waters of the CS in present study. Approach: DO and Chl-a concentrations were analyzed using field measurements data over the southern continental shelf near Iranian coasts. The data were collected at 13 stations along three transects down to 42 m depth in east part of the southern coasts of the CS, off Babolsar in autumn 2008. Results: In the time of measurements, the DO concentrations ranged between 8.4 and 11.2 mg L-1 in the area. Amounts of the Chl-a were varied between 1.3-4.2 mg m-3 with the maximal levels at 15 m depth. The formation and destruction of seasonal thermocline affect the DO and Chl-a concentrations in vertical direction. Conclusion: The collected data present useful knowledge about distributions of DO and Chl-a in the coastal waters of Babolsar and near mouth of Babolrood River. Amounts of DO and Chl-a in the region were under effects of Babolrood River discharge, stratification of water column (seasonal thermocline) and atmospheric processes. The results indicate the need of serious efforts for reducing entrance of human activities wastes and pollutants into the Caspian environment.

Scattering of near‐inertial internal waves along the Japanese coast of the Japan Sea

The scattering of near‐inertial internal waves (NIIWs) induced at the tips of landmasses was investigated by mooring observations using current meters and thermometers in the surface layer along peninsulas and an island located along the Japanese coast of the Japan Sea during the fall of 2006. Signals of NIIWs were found in alongshore currents and in temperatures recorded near the seasonal thermocline. The signals appeared after wind stress had reached a maximum, and they lasted for more than 2 days. Relatively high current energy regions due to NIIWs were localized around the northern parts of the peninsulas and island. The phase lag of the temperature fluctuations increased in the southern regions along the eastern coasts of the peninsulas and island. The generation and propagation of NIIWs were investigated by numerical experiments that used a multilayer level model with realistic topography. Model results showed that NIIWs induced by the wind struck the tips of landmasses and scattered and that NIIWs were trapped by the coast and propagated with characteristics of coastal‐trapped waves (CTWs) and then rapidly attenuated. The CTWs had a distorted current structure at landmass tips because of periodic beam‐like current structures from the seafloor. These signals show that CTWs radiate energy away from the shore as internal waves originating from topographical scattering, which is considered to cause the rapid attenuation of the CTWs.

Net and gross oxygen production from O2/Ar, 17O/16O and 18O/16O ratios

In aquatic systems, variations in the O 2 /Ar ratio and in the 17 O anomaly ( 17 Δ, calculated from 17 O/ 16 O and 18 0/ 16 0) are affected by both physical and biological processes. Laboratory observations suggest that 17 Δ is independent of respiration rate, in contrast to the O 2 /Ar ratio. This makes it possible to determine gross O 2 production from measurements of 17 O/ 16 O and 18 0/ 16 0 of dissolved O 2 , while the O 2 /Ar ratio can be applied to estimate net O 2 production. We demonstrate how biological and physical forcing modifies the O 2 /Ar ratio and 17 Δ during the day and at night in a coral reef near Eilat. This field study confirmed our hypothesis that 17 Δ of dissolved O 2 ( 17 Δ dis ) is affected by photosynthesis, ocean dynamics and air-water gas exchange, but not by respiration. We also show, for the first time, a detailed record of 17 Δ responses to biological fluxes and subtropical ocean dynamics on a seasonal scale. The measurements were conducted in the Atlantic Ocean near Bermuda during monthly cruises of the Bermuda Atlantic Time-series Study (BATS) from March 2000 to January 2001. With the formation of the seasonal thermocline, 17 Δ dis significantly increased below the oceanic mixed layer, reflecting the seasonal integration of photosynthesis in the thermocline. Hence, 17 Δ dis accumulation may be used to calculate the overall rate of photosynthesis below the mixed layer. We used the O 2 /Ar ratio and 17 Δ dis to estimate net and gross O 2 production (NOP and GOP) and directly compared them with production values derived from 14 C incubations. In general, GOP based on 17 Δ dis was several times greater than production determined via 14 C fixation [P( 14 C)], which in turn was somewhat greater than NOP based on the O 2 /Ar ratio. The NOP/GOP ratio was 0.08 to 0.21. This implies that the observed high GOP/P( 14 C) ratios result mainly from rapid cycling of O 2 between photosynthesis and O 2 uptake mechanisms.

Validating and assessing the sensitivity of the climate model with an ocean general circulation model developed at the Institute of Atmospheric Physics, Russian Academy of Sciences

A new version of the Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS), climate model (CM) has been developed using an ocean general circulation model instead of the statistical-dynamical ocean model applied in the previous version. The spatial resolution of the new ocean model is 3° in latitude and 5° in longitude, with 25 unevenly spaced vertical levels. In the previous version of the oceanic model, as in the atmospheric model, the horizontal resolution was 4.5° in latitude and 6° in longitude, with four vertical levels (the upper quasi-homogeneous layer, seasonal thermocline, abyssal ocean, and bottom friction layer). There is no correction for the heat and momentum fluxes between the atmosphere and ocean in the new version of the IAP RAS CM. Numerical experiments with the IAP RAS CM have been performed under current initial and boundary conditions, as well as with an increasing concentration of atmospheric carbon dioxide. The main simulated atmospheric and oceanic fields agree quite well with observational data. The new version’s equilibrium temperature sensitivity to atmospheric CO2 doubling was found to be 2.9 K. This value lies in the mid-range of estimates (2–4.5 K) obtained from simulations with state-of-the-art models of different complexities.